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Next: <a href="Compiler-Characteristics.html#Compiler-Characteristics" accesskey="n" rel="next">Compiler Characteristics</a>, Previous: <a href="Invoking-GNU-Fortran.html#Invoking-GNU-Fortran" accesskey="p" rel="prev">Invoking GNU Fortran</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Runtime_003a-Influencing-runtime-behavior-with-environment-variables"></a>
<h2 class="chapter">3 Runtime:  Influencing runtime behavior with environment variables</h2>
<a name="index-environment-variable-1"></a>

<p>The behavior of the <code>gfortran</code> can be influenced by
environment variables.
</p>
<p>Malformed environment variables are silently ignored.
</p>
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<tr><td align="left" valign="top">&bull; <a href="TMPDIR.html#TMPDIR" accesskey="1">TMPDIR</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Directory for scratch files
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="GFORTRAN_005fSTDIN_005fUNIT.html#GFORTRAN_005fSTDIN_005fUNIT" accesskey="2">GFORTRAN_STDIN_UNIT</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Unit number for standard input
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="GFORTRAN_005fSTDOUT_005fUNIT.html#GFORTRAN_005fSTDOUT_005fUNIT" accesskey="3">GFORTRAN_STDOUT_UNIT</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Unit number for standard output
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="GFORTRAN_005fSTDERR_005fUNIT.html#GFORTRAN_005fSTDERR_005fUNIT" accesskey="4">GFORTRAN_STDERR_UNIT</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Unit number for standard error
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="GFORTRAN_005fUNBUFFERED_005fALL.html#GFORTRAN_005fUNBUFFERED_005fALL" accesskey="5">GFORTRAN_UNBUFFERED_ALL</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Do not buffer I/O for all units
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="GFORTRAN_005fUNBUFFERED_005fPRECONNECTED.html#GFORTRAN_005fUNBUFFERED_005fPRECONNECTED" accesskey="6">GFORTRAN_UNBUFFERED_PRECONNECTED</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Do not buffer I/O for preconnected units.
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="GFORTRAN_005fSHOW_005fLOCUS.html#GFORTRAN_005fSHOW_005fLOCUS" accesskey="7">GFORTRAN_SHOW_LOCUS</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Show location for runtime errors
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="GFORTRAN_005fOPTIONAL_005fPLUS.html#GFORTRAN_005fOPTIONAL_005fPLUS" accesskey="8">GFORTRAN_OPTIONAL_PLUS</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Print leading + where permitted
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="GFORTRAN_005fLIST_005fSEPARATOR.html#GFORTRAN_005fLIST_005fSEPARATOR" accesskey="9">GFORTRAN_LIST_SEPARATOR</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Separator for list output
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="GFORTRAN_005fCONVERT_005fUNIT.html#GFORTRAN_005fCONVERT_005fUNIT">GFORTRAN_CONVERT_UNIT</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Set conversion for unformatted I/O
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="GFORTRAN_005fERROR_005fBACKTRACE.html#GFORTRAN_005fERROR_005fBACKTRACE">GFORTRAN_ERROR_BACKTRACE</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Show backtrace on run-time errors
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="GFORTRAN_005fFORMATTED_005fBUFFER_005fSIZE.html#GFORTRAN_005fFORMATTED_005fBUFFER_005fSIZE">GFORTRAN_FORMATTED_BUFFER_SIZE</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Buffer size for formatted files
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<tr><td align="left" valign="top">&bull; <a href="GFORTRAN_005fUNFORMATTED_005fBUFFER_005fSIZE.html#GFORTRAN_005fUNFORMATTED_005fBUFFER_005fSIZE">GFORTRAN_UNFORMATTED_BUFFER_SIZE</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Buffer size for unformatted files
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